The invention pertains to electrolytic cells, especially mercury chlor-alkali cells with current feed rods or power feed bolts and with current distributors in the form of flat sections standing on-edge a certain distance apart, which are welded at their lower edges to activated electrode elements perpendicular to the current distributor sections. The activated electrode elements consist of flat sections up to 2-mm-thick, standing on-edge, with vertical outside surfaces. The number of individual activated electrode elements is larger than the number of current distributors, the electrode elements being installed with a gap of at least 2 mm between them.
U.S. Pat. No. 4,022,679 describes an electrode for mercury chlor-alkali electrolytic cells with current feed rods or current feed bolts. The electrode has flat sections spaced a certain distance apart, which are connected at their lower edge to activated electrode elements, which are perpendicular to the sections. The number of individual activated electrode elements is larger than the number of power-supplying parts, and the individual elements as seen in cross section, have a tapering lower edge, which is designed essentially in semicircular form. The problem with these circular or semicircular designs has to do with the discharge of the gas bubbles which form during electrolysis, because these bubbles interfere with the exchange of ions in the electrolytic gap between the semicircular sections and the mercury cathode, and yet there is no way for these bubbles to escape quickly. As a result, it must anticipated that a kind of gas bubble "cushion" will form in the lower area of the anode profile.
U.S. Pat. No. 4,364,811 discloses an anode for mercury chlor-alkali electrolytic cells, where the current is supplied by way of a rod or bolt, which is connected to activated electrode elements designed as flat sections, by power distributors in the form of rectangular sections running transversely. The current distribution sections distribute the current and are mounted crosswise to the flat electrode sections. Here, too, there is the danger that a gas cushion will form in the electrode gap or below the lower horizontal edge of the electrode elements, with the result that it becomes impossible for a rapid electrochemical reaction to occur because of the insufficient supply of ions, the reaction itself being hindered by the production of gas. Even though the three conductor planes with optimally dimensioned flat sections leads to a favorable power distribution, there is nevertheless the problem of achieving a rapid electrochemical reaction in the electrode gap and of the interference with this reaction caused by the production of gas bubbles and the formation of a gas cushion.
The problem of the electrochemical reaction also plays an important role in membrane electrolytic cells, as can be seen from EP No. 204,126. To avoid the interference with the transmission of power caused by gas bubbles and to achieve an improvement in the energy efficiency, the electrode elements adjacent to the membrane are provided with recesses. Because these recesses have the effect of increasing the surface area of the activated electrode, they promote a better electrochemical reaction and make it easier for the gas to escape.